This invention relates generally to turbine engines, and more specifically to turbine blades used with turbine engines.
At least some known turbine engines include a turbine that includes a plurality of rotor blades that extract rotational energy from fluid flow entering the turbine. Because the turbine is subjected to high temperatures, turbine components are cooled to reduce thermal stresses that may be induced by the high temperatures. Accordingly, at least some known rotating blades include hollow airfoils that are supplied cooling air through cooling circuits defined within the airfoil. More specifically, the airfoils include a cooling cavity bounded by sidewalls that define the cooling cavity.
To fabricate the cooling passages, at least some known turbine blades are cast using an internal core that forms the internal cooling passageways within the blades. Because of the relative large size of blades and/or vanes that may be used within industrial turbine engines, at least some known cores are reinforced to enable the core to withstand the injection pressures of the wax and the subsequent casting process. More specifically, a tip of at least some known casting cores is supported during the casting process by at least one rod that has a substantially constant diameter along its length.
When the casting process is complete, a print out coupled between the rod and the core is removed. An opening created by the rod may provide a channel for cooling the tip cap portion of the blade. In some known blade designs, the opening is sealed to facilitate cooling other portions of the blade. In such cases, the openings are sealed using known sealing techniques, such as welding or brazing. To facilitate forming a smaller diameter opening, some known castings use rods that have a diameter less than approximately 0.035 inches. However, as an overall size and/or weight of the casting is increased, a smaller diameter rod may not provide enough structural support to the core.